Magnetically operated low resistance fluid flow switch



Feb. 14, 1933. R 5 MNLEY 1,897,485

MAGNETICALLY OPEEATED LOW RESISTANCE FLUID FLOW SWITCH Filed March 21,1931 filly. 2

INVENTOR J H BY C AETTORNEY Patented Feb. 14, 1933 it 1,897,485

UNITED STATES- PATENT OFFICE ROY D. MAILEY, OF EAST ORANGE, NEW JERSEY,ASSIGNOR TO GENERAL ELECTRIC VAPOR LAM? COMPANY, OF HOBOKEN, NEW JERSEY,A CORPORATION OF NEW JERSEY MAGNETICALLY OPERATED LOW RESISTANCE FLUIDFLOW SWITCH Application filed March 21, 1931. Serial No. 524,377.

The present invention relates to fluid flow ance, and thus of minimumheating, it is switches, and especially to magnetically opobvious thatthe fluid path between the inleads erated switches which are adapted foruse should be as short as possible, especially since in circuitscarrying relatively large currents. the effective conducting area of thefluid path The invention consists in a fluid flow switch is limited bypractical considerations, such of novel construction, and in a novelmethod as maximum dimensions for the switch,

of operating the same as hereinafter set forth weight, cost, and thelike. It would thus apand claimed. pear that additional current carryingca- A particular object of the invention is to pacity could be obtainedin a practical switch 10 provide a fluid flow switch having arelativeonly by a sacrifice of the rupturing capacity, 1y large currentcapacity. Another object of with the result that there has beenheretofore the invention is to provide a switch having a more or lessdefinite limit to the capacity a low internal resistance. Still anotherobof commercially practical switches.

ject of the invention is to provide a magneti- I have now discovered,however, that a fluid 15 cally operated switch of simple constructionflow switch of the so-called magnetic type, in having the aforesaidcharacteristics. Anwhich the circuit is opened or closed by disotherobject of the invention is to provide placement of the fluid conductorthrough a fluid flow switch of the magnetic type which magnetic movementof a float, may be so conwill withstand severe jolting. A furtherobstructed that the length of the path which 20 ject of the invention isto provide a novel the current must traverse through the fluid is methodof operating such a fluid flow switch. materially reduced after thecircuit through Other objects and advantages of the inventhe switch hasbeen closed, and again intion will appear from the following detailedcreased before the circuit through the switch specification, or from aninspection of the acis interrupted between fluid pools in the usual 25companying drawing. manner. This new result, which permits ex- Thecurrent rating of electrical switches is tremely large currents to becontinuously cardetermined, as is well known, by two factors; ried in aswitch without any impairment or the current which they can safelyinterrupt, limitation of the current rupturing capacity, and the currentwhich they can continuously is obtained in a very simple manner. Ac-

30 carry without undue heating due to the intercording to a preferredform of my invention so nal resistance thereof. In switches of the fluida metallic bridging member is carried by the flow type the emphasis hasbeen on the first of aforesaid float, whereby said bridging memthesefactors, hence in this type of switch the ber is caused to enter thefluid and reduce the metallic inleads have invariably been spaced lengthof the fluid path which must be trav- 5 a considerable distance apart,in order to perersed by the current'after the circuit through mlt thearc of rupture to be drawn out suflithe switch has been closed by fluidflow. ciently to extinguish it. This construction Thus the internalresistance of the switch is obviously necessitates the use of arelatively very materially reduced, so that large ourlong fluid path tocomplete the circuit through rents can be continuously carried thereby4") the switch when it is in a closed circuit posiwithout undue heating.My new bridging tion. A long fluid path is, however, highly membermoreover also performs another funcundesirable from the standpoint ofthe second tion in a preferred embodiment of my invenfactor mentionedabove, due to the fact that tion. This type of switch is, as is wellknown, any of the fluids which are ordinarily used peculiarly subject todamage by jolts and havearelatively high specific resistance. For shocksdue to the relatively massive parts example, mercury, the fluid almostuniversalwhichare freely movable therein. As a result 1y used, has aspecific resistance which is ap of the serious breakage losses whichhave thus proximately twenty times that of tungsten, been suffered,especially during shipment,

and sixty times that of copper. Hence from when the cushioning effect ofthe fluid could 50 the standpoint of minimum internal resist not berelied upon to prevent rapid movenever gone into extensive use, despitethe chamber 1,

manifest advantages thereof. 1 have now discovered that the resilienceof my new bridging member may be relied upon to absorb any shocks orjolts which would otherwise destroy the vitreous member. As a result, mynew switch not only has a current capacity which is far beyond that ofany switch heretofore proposed of commensurate size, but it also isexceptionally resistant to damage by rough handling, so that it may beshipped without danger of breakage. g

For the purpose of illustrating my invention I have shown twoembodiments thereof in the accompanying drawing, in which Fig. 1 is asectional view of a fluid flow switch of the magnetic type, shown in anopen circuit position, and

Fig. 2 is a sectional view of a modification of the switch of Fig. 1.

In this drawing, with special reference to Fig. 1, there is shown afluid flow switch having a sealed envelope comprising a tubular thevertical tubular extension2 thereof, and two chambers 3 which open intoopposite sides of said tubular chamber 1 near the top thereof. Saidenvolope may be made of any suitable vitreous material, such as lead orlime glass, but where large currents are to be interrupted I prefer touse one of the more refractory vitreous materials, such as aborosilicate glass or fused silica. A cup 4. is formed in each of thechambers 3 at the outer end thereof, in each of which there is retaineda mercury pool 5. An inlead 6,

which is preferably made of tungsten when the switch envelope is made ofa borosilicate glass, is sealed into each of the aforesaid cups inleadextending upwardly to a point just below the surface of one of saidmercury pools mercury pool 7,

on which floats a plunger comprising a tubular body 8 tightly closed atthe bottom by a suitable cap 9 and at the top by the magnetic core 10,said plunger extending into and being freely movable. axially within theupward extension 2 of the aforesaid chamber 1. A coil 11 which ispositioned about the aforesaid extension 2 serves to de ress saidplunger into the mercury 7 at Wlll, raising the level of said mercuryuntil it merges with the pools 5. A. bridging conductor 12 which iscarried by the tubular body 8 extends into each of the chambers 3 to apoint directly above the inleads 6, the ends thereof being preferablyturned downwardly toward said inleads. Said bridging conductor isnormally out of contact with the mercury pools 5, but is moved intocontact therewith after said pools have been merged with the mercurypool 7 further movement of the magnetically operated plunger causing thebridging conductor to make contact with each of the inleads 6, the endsof said 5. The tubular chamber 1 contains a menace bridging conductorand of said inleads preferably being flanged to ensure registry thereofdespite any slight rotational movement of the magnetic plunger. Saidbridging conductor 12 is also preferably curved upwardly toward eachend, so that excessive upward movement of the magnetic plunger will bearrested by these upwardly curved portions of said bridging conductormoving into contact with the vitreous walls of the chamber 3, thus notonly transferring the impact to the portion of the envelope which isbest capable of resisting it, but also utilizing the resilience of thebridging conductor 12 to reduce the severity thereof. In some cases thebridging conductor 12 is flattened out in order to increase thisresilience. The lower end of the tubular body 8 is preferably enclosedin a vitreous sheath comprising a tube 13 which is slipped thereon andwhich is conveniently held in a fixed position against the bridgingconductor 12 by the cap 9. The bridging conductor 12 is ordinarilyformed of tungsten, but in cases where a very low resistance is desiredit is made of a better conductor, such as copper which has been platedor coated with nickel or chromium to prevent contamination of themercury. When the coil 11 is to be energized by'direct current thetubular body 8 and the cap 9 are preferably made either of a metal whichwill not contaminate mercury, such as a chrome-iron alloy, or of anyother suitable metal plated with chromium or the like to preventcontamination of the mercury. When the coil 11 is to be energized by apulsating or alternating current, however, these parts are preferablyformed of porcelain, or an equivalent structure is formed of a suitablevitreous material such as glass, fusedsilica or the like, the vitreoustube 13 then being omitted. The iron core 11 is also preferablylaminated to prevent undue heating thereof, it being convenient toextend the tubular body 8 upwardly in this case to aid in confining the'laminations. A suitable arc suppressing gas, such as hydrogen, issealed within the envelope of the switch.

The switch shown in Fig. 2 has a sealed vitreous envelope in the form ofa tubular chamber 20 with a side chamber 21 opening into the sidethereof at some distance from the bottom. A cup 22 is formed in theouter end of said side chamber 21 in which a pool of mercury 23 isretained. An inlead 24 which is sealed through the bottom of said cupextends nearly to the surface of said mercury pool. An inlead 25 whichis sealed through the upper end of the chamber 20 extends axially withinsaid chamber into the boss 26 on the bottom thereof. Said inleads are oftungsten, or of chromium plated copper, or the like. The chamber 20contains a large pool 27 of mercury, on which floats a cylindricalelectrically conducting body 28. Said conducting body, which may beconveniently formed of chromium plated copper, has a central openingtherein through which passes the inlead 25, said body being freelyslidable thereon. A tube 29 which surrounds the inlead and which isthreaded into the floating body 28 supports at its upper end themagnetic core 30 which likewise has a central opening therein for theinlead 25. A bridging conductor 31 extends from the floating body 28,with which it makes a good electrical contact, into the side chamber 21to a point above the inlead 24, at which point it turns downwardly ashort distance. A coil 32 which extends about the chamber 20 at a pointsomewhat below the normal level of the iron core 30 serves, whenenergized, to attract said core and thereby depress the floating body 28sufliciently to cause the mercury pools 23 and 27 to merge and the endof the bridging conductor 31 to move into contact with the inlead 24.The ends of said inlead and of said bridging member are preferablyflanged to ensure an appreciable area of registry, despite any slightrotation of the floating body 28 which may be permitted by movement ofthe bridging conductor 31 between the walls of the side chamber 21.lVhere desired, however, an additional guide member 33 which isconveniently supported by the inlead 25 is used, said guide memberentering a suitable hole in the core 30, whereby all of the floatingparts are maintained in a fixed rotationalposition. In order to preventthe are of rupture striking to the floating body 28 that portion of theside wall thereof which extends above the mercury 27 is preferablyenclosed in a suitable vitreous sheath. As shown, this is convenientlydone by placing a glass tube 34 about said body, said tube resting on ashoulder on said body and being locked in position by the bridgingconductor 31. The bridging conductor 31 is also utilized to absorb theshocks caused by abnormal movements of the movable parts of the switch,as in the switch shown in Fig. 1, the end portion of this conductorbeing the first to engage the envelope wall upon upward movement. Whenthe coil 32 is to be operated on alternating current, it is obvious thatthe magnetic core 30 should be laminated to reduce eddy current loss,and that the tube 29 should have a slit therein for the same reason. Insome cases it is desirable to mold the core 30 of magnetizable particlesintermixed With any binder which may be easily degassed, instead ofusing the more conventional laminated structure. A suitable arcsuppressing atmosphere, such as'hydrogen, is sealed within the switchenvelope.

In the use and operation of the switch of Fig.1, the switch being in theopen circuit position as shown, upon passage of an electric currentthrough the coil 11 the core 10 is drawn downwardly causing a displace--ment of the mercury 7. The level of the mercury pool 7 thereupon rises,causing said pool to merge with the mercury pools 5. A circuit isthereupon closed between the inleads 6 through a relatively long path inthe mercury. Further movement of the core 10 then causes the bridgingconductor 12 to make contact at each end with the rising mercury, afterwhich still further movement of said core causes the br dging conductorto come into direct contact with the inleads 6, greatly reducing theresistance of the circuit between said inleads. It will be noted thatthe proper sequence of these operations is ensured, due to the fact thatthe mercury must be displaced sufliciently to close the circuit beforethe bridg ng conductor 12 can be depressed enough to make contact withsaid mercury. 'Upondeenergization of the coil 11 the magnetic core isallowed to rise, whereupon the level of the mercury 7 starts to fall.The bridging conductor 12 soon rises above the level of the mercury, butno arc of rupture occurs since a circuit is still' closed between theinleads 6 through the mercury. As said bridging conductor reaches apoint well above said mercury the latter reaches the level at which themercury 7 again separates from the pools 5, with an ensuing arc ofrupture, which usually occurs at one or the other of said pools, as thecircuit through the switch is interrupted, this are of rupture beingrapidly suppressed by the hydrogen atmosphere. The bridging conductorbeing well above the level of the mercury at this time,there is nodanger of the arc striking thereto, while the vitreous tubing13'prevents the are from striking to the tube 8. It is obvious that theseparation between the pools 5 and the pool 7 at the moment of rupturemay be made as long as desired in a switch of my novel construction,without in any way increasing the length of the fluid path traversed bythe current when my sw tch is fully closed. Hence this switch isespecially adapted to operate with extremely large currents, of theorder of 100 amperes or more. Moreover, with a switch constructed asshown and described, any sudden movement of the plunger in an upwarddirection will be arrested by the bridging conductor making contact withthe walls of the chambers 3. Due to the resilience of this bridgingconductorfwh ch need not be very great to be effective, the impact onthe envelope isreduced, and at the same time is directed to a part ofsaid envelope which can best withstand the impact. Similarly, any suddenmovement of the plunger in the opposite direction will be arrested bycontact of the flanged ends of sa d bridging conductor 12 with theinleads 6, said bridging conductor again tending to reduce the shock byvirtue of its resilience. In some leases where it is desired to directthis reduced shock to the enveloperather than to said inlead l omit theflanged ends on said bridging conductor 12, and double the ends of saidconductor back under the main portion thereof, said ends extendinginwardly far enough to make contact with the lower walls of the chambers3 between the cups 4 and the main chamber 1 when the plunger is moveddownwardly. l/Vith this construction said bridging conductor has an evengreater effective length, and therefore greater resiliency, when it isabsorbing downward shocks than it has when it is absorbing upwardshocks, and in addition causes the shock to be directed to a preferredposition of the envelope.' Since the bridging conductor 12 still veryclosely approaches the inleads 6 at the moment its movement is arrestedby contact with the lower wall of the chamber 3, it is obvious that thefluid path traversed by the current in the fully closed position of theswitch is extremely short, and that the switch has, therefore, anextremely low internal resistance, despite this modification. As aresult of this absorption and redirection of shocks my new switch, witheither of these constructions, is singularly immune to damage by roughhandling, such as is ordinarily experienced in transit.

The operation of the switch of Fig. 2 18 similar to that of Fig. 1. Tnthis switch,

- when a current is passed through the coil 32 the magnetic core 30 isdrawn down, forcing the floating body 28 into the mercury 27. The level.of the latter thereupon rises until said pool 27 merges with the pool23. Current thereupon flows from' the inlead 25 through a relativelylong path in the mercury 27 to the inlead 24. Upon further depression ofthe floating body 28 the end of the bridging conductor 31 is moveddownwardly into said mercury and into contact with the inlead 24. Sincethe latter contact is always made below the surface of the mercury it isevident that a good electrical connection is always established.Practically all of the current thereupon flows through the path ofextremely low resistance thus established from the inlead 25 through'ashort path of large area in the mercury 27 to the floating body 28, andthence through the conductor 31 to the inlead 24. This circuit, due toits low resistance, is especially adapted to continuously carry verylarge currents. Upon deenergization of the coil 32 the floating body 28is buoyed up by the mercury 27, carrying the bridging conductor 31 awayfrom the inlead 24, and causing it to move above the level of themercury 27 which is, of course, simultaneously falling. No arc ofrupture occurs at this time, however, due to the fact that a circuit isstill closed between the inleads 24 and 25 through a relatively longfluid ath. As the mercury level continues to fall the pool 27 againseparates from the pool 23,

eena-ea disrupting the circuit through the switch. An arc of rupturethereupon occurs between said pools, this arc, however, being quicklysuppressed by the hydrogen atmosphere. Since the bridging conductor hasbeen raised well above the mercury surface before the circuit is openedthere is no likelihood of this are of rupture striking thereto. Thefloating body 28 is also amply protected from this are by the vitreoustubing 34. It will be obvious, moreover, that the bridging conductor 31functions in the same manner as the bridging conductor 12 of the switchof Fig. 1 in reducing and directing any impacts of the movable parts ofthe switch on the envelope thereof due to rough handling.

While ll havedescribed my invention by reference to specific embodimentsthereof it is to be understood that it is not limited thereto, but thatvarious omissions, substitutions and changes, within the scope of theappended "claims, may be made therein without departing from the spiritof my invention.

T claim as my invention:

1. A fluid flow switch comprising a sealed envelope, inleads sealed intosaid envelope, a conducting fluid in said envelope, the normal level ofsaid fluid being insuflicient to connect said inleads, a body floatingon said fluid, a bridging conductor carried by said floating body, andmeans to depress said body into said fluid at will to connect saidinleads by way of a long fluid path and then to move said bridgingconductor to diminish the length of said path.

2. A mercury switch comprising a sealed envelope, inleads sealed intosaid envelope, mercury in said envelope, the normal level of saidmerc'ury being insuficient to connect said inleads, a body floating onsaid mercury, a resilient bridging conductor carried by saidfloatingbody, and means to depress said body into said fluid at will to connectsaid inleads by way of a long fluid path and then to move said bridgingconductor to diminish the length of said path, a free end of saidbridging conductor serving to limit the movement of said floating body.

3. A fluid flow switch comprising a sealed envelope having a mainchamber and a chamber extending'laterally therefrom, an inlead sealedinto said lateral chamber and another inlead sealed into another part ofsaid envelope, a conducting fluid in saidmain chamher, the normal levelof said fluid being insufficient to connect said inleads, a bodyfloating on saidfluid, a resilient bridging conductor carried by saidfloating body and extending into said lateral chamber, and means todepress said body into said fluid at will to connect said inleads by wayof a long fluid path and then to move said bridging conductor todiminish thelength 'of said path, the end of said bridging conductorwhich extends into said lateral chamber serving to limit the movement ofsaid floating body.

4. A mercury switch comprising a sealed envelope having a main chamberand a chamber extending laterally therefrom, mercury in said mainchamber, an inlead sealed into said lateral chamber and another inleadsealed into another part of said envelope, a body floating on themercury in the main chamber, a bridging conductor carried by saidfloating body and extending into said lateral chamber, and means todepress said body into said mercury at will to connect said inleads byway of a long fluid path and then to move said bridging conductor intocontact with the inlead in said lateral chamber to diminish the lengthof said path.

5. A mercury switch comprising a sealed envelope having a main chamberand two chambers extending laterally therefrom, mercury in said mainchamber, a mercury pool in each of said lateral chambers, an inleadsealed into each of said pools, a body floating on the mercury in saidmain chamber, a bridging conductor carried by said floating body andextending into each of said lateral chambers, and means to depress saidbody into said mercury at will to cause the mercury in said main chamberto merge with said mercury pools, and then to move said bridgingconductor below the surface of the mercury in said lateral chambers.

6. A mercury switch comprising a sealed envelope having a main chamberand two chambers extending laterally therefrom, mercury in said mainchamber, a mercury pool in each of said lateral chambers, an inleadsealed into each of said pools, a body floating on the mercury in saidmain chamber, a resilient bridgin conductor carried by said floatingbody anfextending into each of said lateral-chambers, and means todepress said body into said mercury at will to [cause the mercury insaid main chamber to merge with said mercury pools, and then to movesaid bridging conductor below the surface of the mercury in said lateralchambers, the ends of said bridgin conductor serving to limit themovement of said floating body.

mercury switch comprising a sealed envelope having a main chamber and achamber extending laterally therefrom, mercury in said main chamber, amercury pool in said lateral chamber, an inlead sealed into said mainchamber, an inlead sealed into said mercury pool, a body floating on themercury in said main chamber and extending about the first mentionedinlead, said body being electrically conducting, a bridgin conductorcarried by said floating body and extending into said lateral chamber,and means to depress said floating body into said mercury at will tocause the mercury in said main chamber to merge with said pool and thento move said bridging conductor below the surface of said mercury injuxtaposition to the inlead sealed into the lateral chamber.

8. A mercury switch comprising a sealed envelope having a main chamberand a chamber extending laterally therefrom, mercury in said mainchamber, a mercury pool in said lateral chamber, an inlead sealed intosaid main chamber, an inlead sealed into said mery. Signed at Hoboken,in the county of Hudson and State of New Jersey, this 20th day of March,A. D. 1931.

ROY D. MAILEY.

